The electrostatographic reproduction process for making high quality copies of documents is now well known. For example, in FIG. 1 of Imperial et al U.S. Pat. No. 4,083,093, there is shown a schematic illustration of an automatic xerographic reproducing machine. Briefly, the xerographic reproducing machine includes a photoconductive insulator, sometimes referred to as the photoreceptor, on which the imaging process is to take place. The photoreceptor is successively passed through a series of processing stations at which the following processes take place: at a charging station, where a uniform electrostatic charge is deposited on the photoreceptor; at an exposure station, where a light pattern of an original document to be reproduced is projected onto the charged photoreceptor to form a latent electrostatic image; at a developing station, where the latent electrostatic image is developed with developing material to form a toner powder image; at a transfer station, where the toner powder image is transferred from the photoreceptor to a support sheet; and at a cleaning and discharge station, where the photoreceptor is cleansed of residual toner particles and electrostatic charge. The support sheet carrying the toner powder image is passed through a fusing station where a fuser roll and a pressure roll cooperate to fuse the toner powder image onto the support sheet. For a more detailed explanation of such an xerographic reproducing machine, reference is made to FIG. 1 of said U.S. Pat. No. 4,083,093, and the related disclosure therein.
As indicated in Fitch U.S. Pat. No. 2,807,233, there are uses in the so-called xerographic machines for rollers which are made of an inner-metallic portion and an outer portion of resilient or yielding material having a high electrical resistance. In said Fitch patent, such a roller is shown to be used in the transfer of the toner powder image from the photoreceptor drum onto the print receiving web. In addition, the same patent also shows the use of such a roller as the charging device for charging the photoreceptor drum prior to the exposure of the original to form an electrostatic latent image on the drum. It is clear, therefore, that a roller having an inner portion that is electrically conductive and an outer portion that is resilient and having an appropriately high electrical resistance have several uses in the electrophotographic process. In said Fitch patent, the inner portion is said to be metallic, and the outer portion is said to be made of a layer of soft semiconducting rubber.
In Shelffo U.S. Pat. No. 3,520,604, there is disclosed a transfer roll which is made of a conductive rubber having a resistivity in the range of from 10.sup.16 -10.sup.11 ohm-cm. The pressure applied to the transfer roll during the transfer operations is said to be in the range of from 2 pounds to about 8 pounds per square inch of contact area.
In Dolcimascolo et al U.S. Pat. No. 3,702,482, there is disclosed a biasable transfer member which is made of a rigid hollow cylinder of a conductive metal, such as aluminum or the like, having a relatively thick intermediate blanket of elastomeric material, such as a polyurethane rubber thereon, with a relatively thin outer coating of an elastomeric material, such as a polyurethane available under the tradename "Adiprene" from the duPont Company.
In Meagher U.S. Pat. No. 3,781,105, there is disclosed a transfer roller which is made of a central conductive core or axle, an electrically "relaxable" inner layer, and an outer "self-leveling" layer. The roller defines a nip at the point of transfer through which the transfer member is passed.
In Gundlach U.S. Pat. No. 3,866,572, there is disclosed a foraminous electrostatographic transfer system with a roller electrode having an electrically conductive core, such as a solid metal roller, a thick layer of foraminous open cell material, such as open celled polyurethane foam, and an outer coating, such as a 10 mil layer of polyurethane. The present invention provides an inexpensive foam roll, and the method for making such a roll, which is useful as the roller electrode in the transfer system of said Gundlach patent.
In Maksymiak et al U.S. Pat. No. 3,942,888, there is disclosed a stepped transfer roller having a conductive core and a layer of resilient and electrically semiconductive or relaxable material thereon. The layer of resilient material is made to have two end portions with a diameter slightly larger than the diameter of the central portion, so that mechanical pressure bearing on the roll is protected from the central portion by the two end portions, to result in lower "hollow character" transfer defects.
In Eddy et al U.S. Pat. No. 3,959,573, there is disclosed a biasable member which is made of a conductive core and a layer of hydrophobic elastomeric polyurethane thereon. The biasable member of this patent is said to have minimal sensitivity to relative humidity changes, or to have its resistivity remain substantially unchanged when changes in relative humidity occur.
In Seanor et al U.S. Pat. No. 3,959,574, there is disclosed a biasable member having controlled resistivity. The biasable member of this patent is made of a conductive core having a coating of an elastomeric polyurethane thereon which contains ionic additives capable of altering or controlling the resistivity to within the preferred resistivity range.
In Lentz et al U.S. Pat. No. 4,058,879, there is disclosed butadiene copolymers having a solubilized conductivity control agents incorporated therein, said copolymers are useful in xerographic devices where control of conductivity and/or relaxation behavior is important.
In Safford et al U.S. Pat. No. 4,062,812, there is disclosed a method for expending the electrical life of copolymers of butadiene and terminally unsaturated hydrocarbon nitriles by incorporating salts having asymmetrical quaternary ammonium cations or salts having structural charge specific anions therein.
Finally, in Lentz et al U.S. Pat. No. 4,116,894, there is disclosed butadiene copolymers having solubilized conductivity control agents incorporated therein, and that the electrical life of such copolymers can be enhanced by varying specified quantities of terminally unsaturated hydrocarbon nitriles in the copolymers.
From the foregoing, it can be seen that there is a continuing need for improved conformable rolls for use in the electrostatographic reproducing process and machines, which are inexpensive to make, which possess the requisite conductivity in the core or central portions, and which have the requisite electrical resistivity in the outer portion or layer.
These and other objects of the invention can be gathered from the following disclosure.